Therapy x-ray system



ILA

m M R m 5 N A R T R. L. WRIGHT ET AL THERAPY X-RAY SYSTEM Filed Sept. '7, 1950 TIME "4 $ECOND5 50 VOLTs Sept. 16, 1952 INVENTORS R. L. WRIGHT. M. E. HAYES L $6? ATTORNEY 1 KV. IN man TENSION TR NsF:

TIME "4 SECONDS Patented Sept. 16, 1952 :Robert L.. Wright, North Linthicumlfleights and .Martin E. Hayes, .Anne Aruntlelv County, Md,, .assignors to Westinghouse: ElectricxCorpora: .tion, East Pittsburgh, Pa, a corporation *of "Pennsylvania 7 Application; September 7, 1950,.SeriatNo. 183*,578

6 Claims.

fIhe-present;inventionv relates. to X-ray systems and...-particularly .to .such..systems used .for the administration. either any treatments.

.An .-X-.-ray, therapy .system necessarily. operates atrelatively. high voltagesranging from two hundred- -to: several. hundred. kilovol-ts. applied toathe Xeray tube, so that the. generatedZXEray beam hasthe .desiredpenetrative value toureach deepseatedN-growthswithin thelhodyof apatient. It has. long-.been.-recognizedinthe art. that the full operating. voltage. cannotlbeimmediatel applied tov .atherapy .X=ray tube without danger of destroying-the tuber .Acoordihgly,. it is. desirableto gradually apply .the voltage to the-X-ray tube. Brier. to. the.presentiinvention, the. voltage has been increased; by manuallymoving-a, largerheostatlfrom .ajhig'h value, to Zero, thus...increasing the. voltage applied. .to the .primaryflof. the high voltage transformer with. an. attendant. increase in thelkil'ovolta e applied to. the. therapy X-ray tube. "Such .me'thddjl is unsatisfactory because it is. diihciiltfor theope'rator to do andresults ina varlabl'eftime.ofvoltagejapplication.

A still;furthermethodlutilized,. and .which eliminates'theabove noted disadvantages, .is to .employ several. stcps-of..resistance.in series and to short-.outssection's of, this resistance with either switches..or .relays, operated by time. delay cams. Howeven. latter arrangement. is. subject to the. .disadvantagesfithat the switchesv .too frequentlvstick an'dlthe. relay contacts, are burned and shortly destroyed by the. are formed at their separation. 'ZMorenventhe. voltage is increased in jumpsrather thanata smooth rate.

Itii'saceordihgly ;the object. of the present, in.- vention. to. prov-idea, therapy lX-ray system in violtageis automatically and. gradually apnli'edtotheIX-ray tube in a smoothmanner.

.Another object.of;.the,present.invention is. the

provisionofa therapy Dhray system whichis electronically econtrolled .to cause. a. gradual .and smoothapplication. oflthe. .vnltage. .to. .the..X=ray tuber .StilLIfurther. objects of the. present. invention will become ohyiousto thoseskilledinthe. art by reference" to the, accompanying drawing wherein:

i'Elg. .I. is -.a diagrammatic illustration of a therapyfhray system constructed. inacoord'ance witlithepresent invention;

.Fig. 21s a graphic illustration oi the. biasing voitage' appliedrto the control grid-of. the electronic tubeemploye'cl. in. the. system otFig. .1. and whereinjthe abscissa represents. time. in seconds andthe ordinate biasing. voltage;

Rig. 3 a graphic I illustration showing the curve; of .theLD.,.fC2;. currentlappliedto"the reactor which .formsoa .part. .of. .thesystem of Figel and wherein the abscissa. againrepresents. time in seconds, andthe. ordinate D'LJC. current;

.4. ..a graphic. illustration. showing. the curve .of thakilovoltage .as appliedlto' the. X-ray tube. of. landwhereinthe. abscissa represents time in secondsandthe-ordinate.kilovoltage.

Referring now .tothe Idrawingin detail, the system .as-shown in Eighlecompr'ises an-TX-ray tube .5...c.onnected. through the customary therapy energizing circuitinclud-ihg. a 'full-waverectifying and high-voltage. condenser bank arrangement 36, to the high voltage-secondary winding] .of. a transformer .8. The. rectifying arrangement .6, however, .may be .of the. well known .half-wave Villard or .Grenacher type if desired.v .The primary winding 9 of the transformer. 8;is.connecte'd .throughltheA. .C. windings. 1.0. of a saturablereactor l2, .to adjustable vvoltage.-regulatin gtaps l3 and. [4: of. anauto transformer I 5, uponclosu'r.e of. normally opencontacts. i6 of.a.relay L1. This relay 1. 1 receives..energyjfromappropriate voltage tapson the. auto-transformer. 15. upon operation of aitimer l.-8 whenfthe .X-ray. on. .switch l9.is closed. by a. technician... The auto-transformer l5 receives its energy Ifrom. a souhcellI-LZ offlthe customary commercial pOtentiaLofLlIE-QSD. volts.

TheD. C. winding,"20-.of. the .saturable reactor .l.2;is connectedtoi-a directeurrent source.B+\ and B. of approximately BOO-40.0. .vlts, .upon .an electron discharge tubelz becoming conductive by operation of .its control .grid '23. .Brior to energizationoflthe X-ray tube 5,; this control" grid 23 is normally biased by a voltagemotapproxh mately 50 volts from all. C. supply-.sourceC- through normally closed contacts 24 of relay 1.1, with the positive terminal .of this. latterwsource being grounded in the same manner-.as one.- side of the D.C..source;B.-,.andhence both suchD; C. sourcesare connectedto theca-thodeifi of electrendischaizge. tube 2-2 by thetground connection G1.. .Connected betwen; the-grid '23 and. cathode 25 in parallel with-leach other isaresistance. .26 andoapaci-tance;1211101712.purpose: to be hereinafter described,-

lPhesystem as above: described opera-tesvin the following manner: upon the closure of. suitable switches-(n01? shown). to makethe-two D.'C. sup.- ply sourcesand .the. source Ll-1L2' eeifectivega negative bias of approximately --50 volts with respect to the cathode is applied: .tothe: grid 23.- of the .electronedischarge tube:.2-.2-;because-centacts 24 are-normally closed. .Such biasing-voltage is sufiicientl-y" high: that nocurrent at this time will flow through the tube 22 nor D. C. winding 28 of saturable reactor l2. This same voltage, however, charges capacitance 21 to the full 50 volts of the D. C. supply source C and the system is ready for operation. The technician then sets the timer i8 for the desired period of treatment and closes the X-ray on switch l9. Closure of this switch immediately energizes relay I l causing it to open its normally closed contacts 25 and to close the normally open contacts l6.

Naturally, the opening of the normally closed contacts 24 disconnects the grid 23 of electron discharge tube 22 from the -50 volt source of supply C. However, the biasing voltage applied to the grid 23 is not immediately altered, since a biasing voltage of -50 volts is still applied to the grid 23 by capacitance 2-1. appreciated from the graphic illustration of Fig. 2. Prior to operation of the X-ray on switch 19, the 50 volts supplied to the grid 23 of the tube 22 from the source C is represented bythe straight horizontal portion of the curve of Fig. 2. However, upon closure of switch 19 and opening of relay contacts 24 which corresponds to zero time, a voltage of 50 volts is still momentarily applied to the grid 23 by capacitance 21, as above mentioned. The capacitance 21 immediately begins to discharge through the resistance 26 with the rate of such discharge being determined by the value of the resistance 26. The latter is so selected that at the expiration of about six seconds, as shown by the curve of Fig. 2, the biasing voltage applied to the grid 23 will have decreased from the -'50 volts to about -17 volts which is the voltage at which tube 22 becomes fully conductive. Thus there-is an automatic and gradually smooth decrease in the biasing voltage applied to the grid 23.

It will also be appreciated that upon operation of relay I! with attendant closure of normally open contacts I 6, a voltage will be supplied to the primary winding 9 of high voltage transformer 8, at a value determined by the setting of the adjustable contacts 13 and I4, which passes through the A. C. windings I of the saturable reactor l2. At the instant of closure of contacts [6 (or zero time as shown in Fig. 2) the grid 23 of the electron discharge tube 22 will, as above noted, still receive its maximum biasing voltageof 50 volts which precludes the fiow of D. C. current from the source of supply 3+ and B through the D. C. winding 20 of the saturable reactor l2. As a consequence, the saturable reactor has a high impedance at the instant of closing switch l9 with attendant closure of relay contacts l6, so 4 that the kilovoltage supplied to X-ray tube 5 by the secondary winding I is still at low value at "zero time as can be seen from the graphic illustration of Fig. 4.

However, as the biasing voltage applied to the grid 23 decreases, as shown in Fig. 2, the flow of D. C. current through D. C. winding of saturable reactor [2 from the supply source 3+ and 3- will increase in the mariner shown in Fig. 3 so that upon the grid 23 reaching the potential of the cathode 25 of about 17 volts in about six seconds, the D. C. current will thereafter remain constant as shown in Fig. 3. Simultaneously with such rise in D. C. current through D. C. winding 20 the impedance of the saturable reactor I2 is reduced, so that the voltage applied to the primary winding 9 and hence to the high tension secondary winding 1 is increased from low starting value at zero time" to the maximum kilovoltage desired and as set by the adjustable con- This may be 4 tacts l3 and I4, following the curve of Fig. 4.

It will thus become obvious to those skilled in the art that a therapy X-ray system is herein provided which is entirely automatic in its operation of gradually and smoothlyapplying the full voltage to a therapy X-ray tube thus eliminating the human element formerly utilized together with a variance in the time delay between energization of the tube and the application of full kilovoltage thereto.

Although one specific embodiment of the present invention has been shown and described, it is to be understood that still further modifications thereof may be made without departing from the spirit and scope of the appended claims.

We claim:

1. Atherapy X-ray system for gradually and smoothly applying full voltage to the tube comprising a therapy X-ray tube, a circuit for energizing said X-ray tube embodying a reactor provided with a saturable magnetic core and initially having a high impedance to decrease the voltage supplied to said X-ray tube, a saturating winding on said core, an electron discharge tube provided with a control electrode and operable when conducting to supply direct current to said saturating winding to decrease the impedance of said reactor, a circuit for supplying a biasing potential to the control electrode of said electron discharge tubeto render the latter initially non-conductive and including energy storage means in shunt with said control electrode, and switching means operable to simultaneously cause closure of the energizing circuit for said X-ray tube and opening of the biasing circuit for said control electrode'with an attendant momentary continued application of a biasing potential to said control electrode from said energy storage means which biasing potential gradually and smoothly decreases as the energy from said storage means dissipates, thereby rendering said electron discharge tube conductive with an accompanying flow of current to said saturating winding and causing a simultaneous decrease in the impedance of said reactor with an attendant gradual and smooth increase in the voltage supplied to said X-ray tube.

2. A therapy X-ray system for gradually and smoothly applying full voltage to the tube comprising a therapy X-ray tube, an excitation circuit for said X-ray tube including a high tension transformer having its secondary winding connected through a rectifying arrangement to said X-ray tube for supplying unidirectional current to the latter, inductive means connected to the primary winding of said high tension transformer and initially having a high impedance to decrease the voltage supplied by the secondary Winding to said X-ray tube and operable upon the application of a unidirectional component thereto to decrease its impedance with an attendant increase in the voltage supplied to said X-ray tube, an electron discharge tube provided with a control electrode and operable when conductive to supply a' unidirectional current component to said inductive means, a circuit for supplying a biasing potential to the control electrode of said electron discharge tube to render the latter initially non-conductive and including energy storage means in shunt with said control electrode, and switching means operable to simultaneously cause operation of said excitation circuit with energization of said X-ray tube and interruption of said biasing circuit for said control electrode with an attendant momentary continued application of a biasing potential to said control electro dedronrsaidsenergystorage meansnvhichrbiaser ing potential-1g-radiiallyjandismoothly-:decreases1.

as theenergy ffomrsaidsstorage means dissipates thereby: rendering;- saidi electron discharge tube conductive to cause a decrease in the impedance of said inductive meansaccompanied by a gradual: and :smooth increaseiin .the -voltage supplied to said X-ray tube. V

3. A therapy.X1ray.system fongradually and smoothly applying'fullvoltage to'the tube comprising 'a therapy X-ray tubeyan excitationicire cuitfor said: X-ray tube includingsa high tension transformer "having its secon'dars swindinggcon e neoted -through airectif-yingsarrangement i to.- said X ray tu'be for supplying unidirectional current to the latter, inductive means connected to the primary winding of said high tension transformer and initially having a high impedance to decrease the voltage supplied by the secondary winding to said X-ray tube and operable upon the imposition of a unidirectional current component thereto to decrease its impedance with an attendant increase in the voltage supplied to said X-ray tube, an electron discharge tube provided with a control electrode and operable when conductive to supply a unidirectional current component to said inductive means, a circuit for supplying a biasing potential to the control electrode of said electron discharge tube to render the latter ini tially non-conductive and including energy storage means in shunt with said control electrode, a relay operable upon energization thereof to simultaneously cause operation of said excitation circuit with energization of said X-ray tube and interruption of said biasing circuit for said control electrode with an attendant momentary continued application of a biasing potential to said control electrode from said energy storage means which biasing potential gradually and smoothly decreases as the energy from said storage means dissipates thereby rendering said electron discharge tube conductive to cause a decrease in the impedance of said inductive means accompanied by a gradual and smooth increase in the voltage supplied to said X-ray tube, and timing means operable to cause energization of said relay for selected time periods.

4. A therapy X-ray system for gradually and smoothly applying full voltage to the tube comprising a therapy X-ray tube energizable from a high potential source of supply including a transformer having a primary winding, a saturable reactor provided with A. C. windings in series with the primary winding of said transformer during energization of said -X-ray tube and initially having a high impedance to momentarily reduce the voltage applied to said primary winding and hence to said X-ray tube upon initial energization of the latter, a D. C. winding on said saturable reactor and operable when energized to reduce the impedance of. said saturable reactor to cause an attendant increase in the voltage applied to said primary winding and hence the kilovoltage applied to said X-ray tube, a D. C. source of supply for said D. C. winding, an electron discharge tube provided with a control electrode and interposed between said D. C. winding and said D. C. supply source to cause energization of said D. C'. winding upon said electron discharge tube becoming conductive, a source of biasing voltage normally applied to the control electrode of said electron discharge tube to render it initially non-conductive and to prevent energization of said D. C. winding, means including capacitance and resistance normally connected gization'l 01% J said'ir-therapyr'X-ray 6.? tonaidseurceaotibiasingiyoltageand in; electrical i parallel;iwith-=.-meanssoperableetopcauseethesenere tube and; the; simultanecus.ni'sconnectionxofisaid source-of biase ingz, voltageefromrthel control.; electrode of: said electronn discharge; tube: with an": attendant. mcmentaryr continued; application? of, a ;biasing voltageeto ithfi econtrol electrode from sa-iimeans which:voltagesgraduallmand smoothly; decreases toreauseesaidielectronmischargeetubeeto,become conductive with: iargradually; smooth, :rise: in -cur rent cthrough said'D; .CI-J windingand:;a- 511111117..- taneouargraduallyjgsmoothzzincrease ;in.;theckiloevoltagersuppiied to:said;therapyXerayitub 5. A therapy X-ray system for gradually and smoothly applying full voltage to the tube comprising a therapy X-ray tube energizable from a high potential source of supply including a transformer having a primary winding, a saturable'reactor provided with A. C. windings in series with the primary winding of said transformer during energization of said X-ray tube and initially having a high impedance to momentarily reduce the voltage applied to said primary winding and hence to said X-ray tube upon initial energization of the latter, a D. C. winding on said saturable reactor and operable when energized to reduce the impedance of said satur able reactor to cause an attendant increase in the voltage applied to said primary winding and hence the kilovoltage applied to said X-ray tube, a D. C. source of supply for said D. C. winding, an electron discharge tube provided with a control electrode and interposed between said D. C. winding and said D. C. supply source to cause energization of said D. C. winding upon said electron discharge tube becoming conductive, a source of biasing voltage normally applied to the control electrode of said electron discharge tube to render it initially non-conductive and to prevent energization of said D. C. winding, means including capacitance and resistance normally connected to said source of biasing voltage and in electrical parallel with the control electrode of said electron discharge tube, a relay operable upon energization thereof to cause the energization of said therapy X-ray tube and the simultaneous disconnection of said source of biasing voltage from the control electrode of said electron discharge tube with an attendant momentary continued application of a biasing voltage to the control electrode from said means which voltage gradually and smoothly decreases to cause said electron discharge tube to become conductive with a gradually smooth rise in current through said D. C. winding and a simultaneous gradually smooth increase in the kilovoltage supplied to said therapy X-ray tube, timing means for causing energization of said relay for selected time periods, and a switch operable upon closure thereof to initiate operation of said timing means.

6. An X-ray system in which full voltage is gradually and smoothly applied to the X-ray tube, comprising an X-ray tube, a circuit for energizing said X-ray tube embodying a reactor provided with a saturable magnetic core and initially having a high impedance to limit the voltage supplied to said X-ray tube, a saturating winding on said core, an electron discharge tube provided with a control electrode and operable when conducting to supply direct current to said saturating winding to decrease the impedance of said reactor, 3, time constant network connected in the control electrode-cathode circuit 7 of said electron discharge tube such that when said network is charged, said'electron discharge device is rendered non-conductive, means for charging said network, and switching means operable to substantially simultaneously cause closure of the energizing circuit for said X-ray tube and opening of the charging means for said network, whereby the biasing potential on said control electrode gradually decreases as the energy stored in said network is dissipated, there-- by rendering the electron discharge tube conductive with an accompanying flow of current to said saturating winding and causing a simultaneous decrease in the impedance of said reactor with an attendant gradual and smooth increase in the voltage supplied to said X-ray tube.

ROBERT L. WRIGHT. MARTIN E. HAYES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,379,125 Weisglass June 26, 1945 2,492,304 Lundahl et a1 Dec. 27, 1949 2,494,218 Weisglass Jan. 10, 1950 15 2,503,075 Smith Apr. 4, 1950 

